DESCRIPTION: The primary focus of this project is to apply recent advances made in magnetic resonance imaging (MRI) and MR angiography (MRA) to the problem of accurate depiction and diagnosis of cervical carotid artery disease. The investigators have developed a special purpose 4 element phased array coil and a set of white blood and black blood imaging techniques which are optimized for yielding very high quality, high resolution images of the cervical carotid artery anatomy and flow. They believe that their high resolution imaging technique will provide the best measures of carotid disease significance. In this study, they will compare the accuracy of these high resolution MRI and MRA techniques in the depiction of the disease using the endarterectomy sample removed en bloc as the truth standard. They will test whether the relative measurements obtained from MRI and MRA are more accurate than x-ray angiography and duplex ultrasound in providing clinically significant measurements of stenosis and plaque burden. This study is configured to complement their involvement in the ACSCEPT protocol (Assessment of carotid stenosis by comparison with endarterectomy plaque trial) and increase the information to be obtained from this study. Patients studied as part of the ACSCEPT evaluation of standardized MRA techniques will also be enrolled in our study of high resolution MRA and MRA efficacy. The morphological measurements of lumen and plaque made from excised endarterectomy sample will be the truth standard for the high resolution techniques. Other surgical patients and non-surgical patients with documented disease will be followed with high resolution MRI and MRA to study the correlation of morphological findings with the onset of clinical symptoms. Although the primary focus of this study will be to assess the diagnostic efficacy of morphological measurements obtained from MRI/MRA, the work will also begin to assemble qualitative assessments of plaque appearance on the images and examine the correlation between those assessments and histological findings.